The alleged Russian spying plot uncovered in the United States has extended to Britain after it was revealed that key players had UK connections.

The US Justice Department released the report on Monday announcing that authorities had busted a spy ring suspected of conducting long-term, "deep-cover" espionage for Moscow.

FBI said it arrested 10 of the alleged spies, including four couples, inside the US on Sunday. A Canadian man believed to be the 11th member of the spy ring was detained in Cyprus while travelling with a US passport.

US authorities assert that the alleged spies were smuggling information using a combination of modern technology and classic spy tricks, including invisible ink and coded messages.

The British Foreign Office confirmed on Tuesday that it was investigating how Tracey Ann Foley, one of the alleged spies, obtained a British passport.

The FBI claimed that Russian handlers had given Foley forged British documents to travel to and from Moscow more easily.

Another alleged spy, identified as Anna Chapman, was said to have an English husband whom she had divorced. The 28-year-old Chapman apparently worked for London-based company Navigator.

A third detainee, salesman Donald Howard Heathfield, who is also Foley's partner, was reported to be in contact with a subsidiary group of Oxford University, the Oxford Futures Forum.

A Foreign Office spokesman asserted, "We are aware that the indictments state that one of the accused has travelled on a UK passport. We will be investigating this fully with the US. We remain confident that the British passport is one of the most secure documents of its kind, fully meeting rigorous international standards.”

Although the Foreign Office refused to comment in detail, it raised the possibility of Russian agents being active on British soil. Three years ago, Britain clashed with Moscow over the fatal poisoning of former KGB agent Alexander Litvinenko in London. Moscow has repeatedly refused to hand over another agent suspected of involvement in Litvnenko's murder.

Last night, the US and Russia were heading for a Cold War-style row over the affair, which began with the arrests of the alleged spies.

Meanwhile, a White House spokesman said President Barack Obama knew about the spy investigation before he met with Russian President Dmitry Medvedev in Washington late last week, but did not mention it during their talks.